Long term objectives: Specificity in the cellular immune system is controlled and regulated by the T cell receptor (TCR), which specifically recognizes peptide/Major histocompatability complex (MHC) molecules. By using recombinant DNA and antibody engineering approaches, we developed a unique approach to rapidly identify and isolate unique antibodies, called T-Cell Receptor-Like antibodies (TCRLs), which recognize and bind to tumor-associated MHC-peptide complexes normally recognized by killer T-cells (CTLs). This affords us the opportunity to transform the unique specificity of tumor CTLs into high affinity soluble recombinant antibodies. TCRL antibodies offer important advantages over CTLs. TCRL antibodies combine the best features of both arms of the immune system: 1) the ability of antibodies to bind with high affinity as soluble molecules not susceptible to the regulatory influences that limit T cells, 2) and the ability of T cells to use the MHC internal surveillance mechanism to detect, from the outside of the cells, any foreign or abnormal protein within any cell in the body. The long term objectives of the proposed research are to evaluate the potential of melanoma-specific TCR-like antibodies to serve as a targeting moiety and/or effector molecule that may potentiate a better immune activity and potentially be developed as a new immunotherapeutic modality for melanoma. Specific Aims: The specific aims that we would like to achieve in this grant application include:1)To evaluate the targeting potential of melanoma specific Toxin-armed TCR-like antibodies recombinant fragments in vitro and in vivo 2)To evaluate the in vitro and in vivo biological activities of melanoma specific TCR-like antibodies as whole antibody molecules 3)To elucidate the molecules events and signal transduction pathways that lead to the biological activities of TCR-like antibodies on melanoma tumor cells. Research & Development Methods: We have developed a large panel of TCRL antibodies targeting various melanoma-specific T cell epitopes derived from several melanoma differentiation antigens. Using these characterized molecules we will explore their biological properties as recombinant antibody fragments and as whole antibodies and evaluate their therapeutic potential in vitro as well as in animal models.